This invention relates to the formation of metal layers on semiconductor bodies.
In the manufacture of semiconductor devices conventional techniques for depositing metal layers, such as electrical contacts, on semiconductor material include evaporation, sputtering and electroplating with evaporation being the most frequently used. One problem encountered is the formation of a rectifying junction between the metal layer and the semiconductor (e.g., between Au or Pt and GaAs) when an ohmic contact is desired. Conversion of the rectifying contact to an ohmic one is usually effected by an alloying procedure. unfortunately, these procedures entail heating the entire semiconductor body of the device and can be detrimental to device performance. Another problem is that the spatial resolution (i.e., conductor linewidth) is limited by the resolution of masks used to pattern the metal layers.
Recently laser induced chemical reactions on semiconductor surfaces have received much attention for possible use in electronic device fabrication. Both laser induced deposition of metals on GaAs and laser induced etching of GaAs and InP have been reported. These investigations involve ultraviolet laser photolysis of gas phase organometallic (for metal depositions) and of gas and liquid phase halogen-containing compounds (for etching). In laser photolysis the laser radiation is absorbed by the gas/liquid phase causing the gas/liquid to decompose into molecular or atomic fragments. These fragments produced by irradiation migrate to the semiconductor surface where they react with the semiconductor material.